A heat dissipator having a heat-conducting substrate and a plurality of heat-dissipating columns is disclosed. The heat-conducting substrate is opened with a plurality of through-holes. Each of the heat-dissipating columns is discretely set on a surface of the heat-conducting substrate. An illuminator having the heat dissipator and an LED illuminating module is also disclosed. The LED illuminating module is fixed on the heat-conducting substrate and includes a circuit board and a plurality of LEDs arranged on the circuit board. This arrangement can increase the surface area for heat exchange with surrounding air and enhance the heat-dissipating efficiency of the heat dissipator.